C3TD879 is an inhibitor of citron kinase ( CITK ), an AGC family serine/threonine kinase that regulates cytokinesis. C3TD879 inhibits CITK catalytic activity with an IC 50 of 12 nM. C3TD879 does not induce CITK knockdown effects on cell proliferation, cell cycle progression, or cytokinesis, but rather reduces the activity by directly binding full-length human CITK (NanoBRET Kd< 10 nM).